This application claims the priority of European patent document 00115375.8, filed Jul. 15, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an ignition system for a combustion chamber of a rocket engine.
Ignition systems of the generic type are known for example, from German Patent Document DE 23 00 983 and can basically be used in all types of rocket engines. They are particularly useful, however, in rocket engines with liquid fuels.
European Patent Document EP 0 953 759 also describes a rocket engine ignition system whose operating condition depends considerably on the operating condition of the rocket engine itself, because the oxidant required for the ignition system is supplied by the rocket engine. For this purpose, complex coordination of the operating conditions is required.
With reference to FIG. 2, German Patent Document DE 23 00 983 describes an ignition system which has a fuel tank for one fuel constituent. By means of feed pipes, a first fuel constituent is introduced into the fuel tank of the second fuel constituent and is mixed there with the latter. Subsequently, controlled by valves, the mixed fuel constituents are fed in a joint feed pipe to an igniter.
It is a disadvantage of this prior art that, as a result of the early mixing of the fuel constituents, a dangerous mixture is created which has to be transported to the igniter along an unnecessarily long path. Also, relatively high expenditures are required for the refueling of the ignition system with the required fuel constituents.
It is therefore an object of the present invention to provide an improved and technically uncomplicated ignition system which ensures higher safety.
This and other objects and advantages are achieved by the ignition system for combustion chambers of rocket engines according to the invention, which has a first fuel tank for a first fuel constituent and a second fuel tank for a second fuel constituent, both of which are separated from the fuel tanks of the rocket engine. Thus, the conditions for the fuel constituents of the ignition system can be adjusted and optimized separately from those of the rocket engine. As a result, an adjustment of the operating conditions of the ignition system is also facilitated because it can take place completely independently of the operating conditions of the rocket engine.
Furthermore, the ignition system comprises an igniter and feed pipes for the respective fuel constituent arranged between the igniter and of the fuel tanks. As a result, it is ensured that mixing of the fuel constituents takes place at the latest possible point in time, specifically only inside the igniter. As a result, a higher operating safety of the system can be ensured.
In this case, the ignition system can, in particular, be designed such that several consecutive ignitions can take place. This can, for example, be implemented by a corresponding design for the control of the ignition system (especially of the switching and control devices provided there, such as valves or the like). As a result, the combustion chamber can be switched off again after a first ignition, and thus a first operation, and can be started again by a new ignition by means of the ignition system. The ignition system according to the invention is particularly suitable for such an application because, depending on the respective application situation, a different number and type of ignitions may become necessary. Because the ignition system can be adjusted independently of the operating conditions of the rocket engine, it is possible to adapt the ignition system to the individual necessities, specifically for multiple ignitions.
As a further feature of the present invention, it is provided that, for regulating the pressure, at least one restrictor is provided in each of the feed pipes. Regulation of pressure in this case therefore does not take place by a pressure control device, such as a control valve with a pertaining electronic control system, as is conceivable per se; rather, much simpler passive elements are used which are therefore also less susceptible to disturbances. Thus, in addition to a constructional simplification, such simpler passive elements contribute to an increased operating safety. The restrictors can either be fixedly installed so that they always generate a certain pressure regulation, or they may have an exchangeable construction, so that an adaption of the pressure regulation can take place to the respective actual situations of the planned operating conditions of the ignition system. The flow-through effect of restrictors is basically known from the field of hydrodynamics, as described, for example in H. Zoebl, J. Kruschik, xe2x80x9cFlow through Pipes and Valvesxe2x80x9d, Springer Publishers Wien, N.Y., 1982, Page 72.
Furthermore, it can be provided that the fuel tanks have an exchangeable construction. Thus, on the one hand, a simple refilling of the fuel tanks can take place outside the ignition system, whereby the constructional expenditures of the ignition system are also reduced because refilling feeds are unnecessary. On the other hand, as a result of the appropriate selection of the fuel tanks, a flexible adaptation of the ignition system to the data of the planned operating conditions can take place, for example, by the selection of different fuels or by providing larger or smaller fuel tanks. In particular, this can also result in a suitable adaptation of the ignition system to different types and numbers of multiple ignitions.
In order to open up the flow of the fuel constituents in the feed pipes and optionally prevent this flow again, it is at least one shut-off valve is preferably provided in each feed pipe. These valves can have a very simple design because they need only take up the open and closed conditions; high-expenditure triggering and control, for example for regulating the pressure, is not required.
In particular, the ignition system can be further developed such that each feed pipe is connected with a rinsing and ventilating system. In the case of the ventilation, a quantity of fuel constituents still remaining after the ignition has taken place can be removed from the ignition system and, particularly in the case of an interruption of the starting operation of the carrier system with which the ignition system is interacting, the fuel can be removed in a simple manner from the ignition system. The rinsing capability can be used for rinsing the ignition system with a cleaning gas or basically also with a suitable liquid in order to remove any residue of the fuel constituents from the ignition system and, for example, prevent a formation of ice in the ignition system. Basically, for each of the feed pipes, a separate rinsing and ventilating system can be provided. However, for reasons of simplicity, it is useful to provide a common rinsing and ventilating system.
Furthermore, the feed pipes may have at least one return valve in order to prevent the fuel constituents from flowing back in the direction of the fuel tanks in the feed pipes, particularly after these had already been mixed in the igniter. Such a return flow could otherwise be triggered, for example, by pressure waves in the combustion chamber. As a result, penetration of undesirable substances (particularly of moisture) into the feed pipes and the fuel tanks can be prevented.
For controlling the function of the shut-off valves and for monitoring the operating behavior of the ignition system, it can be provided, in particular, that the feed pipes are connected with devices for determining the pressure and/or the temperature in the feed pipes.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.